A common application of needle-bearing syringes is to draw medicament or drug-laden solutions into the syringes for administration into a human subject via subcutaneous, intra-muscular and/or intravenous injection. Hypodermic needles and the like are used to perform the tissue penetration and solution administration event. Often times, the solutions are prepared by dissolving a drug in pill, tablet or powder form into an aqueous solvent. The implements used to make the pharmaceutical preparations range from rather sophisticated lab apparatuses in aseptic conditions to more primitive arrangements in which a spoon or like device is used as a mixing vessel with or without the application of heat. In the latter setting, the possibility for solution contamination via environmental factors, e.g., sneezing, coughing, contaminating touching, is considerable.
Apart from the possibility of environmental contamination, the substances used to make the solutions may also pose contamination risks. Although pills and tablets and other powder-based medicaments and medications are designed for relatively safe administration via the alimentary tract, infusion of the same pharmaceutical preparations via hypodermic needle and the like creates a different biological and physiological dynamic in which what is in one setting a safely ingested material becomes a potentially lethal contaminant.
As is well known in the art, drugs in one form or another, but particularly in pill form, are often prepared with waxes, chalky substances, binders, fillers and other additives to ease mechanical ingestion, or to control drug delivery release time, among other functions. Although innocuous substances in the alimentary tract, these same substances can easily be described as undesirable for hypodermic needle injection.
A yet further source of potential solution contamination is the use of needle-bearing syringes for recreational drug use. Apart from the various potential sources of contamination described herein, “needle sharing” adds a significant additional source of potentially lethal contamination. Although biological pathogens may be introduced at any stage of the solution preparation process, transmission of pathogens from one person to another is greatly increased with the use of the same solution with previously used needles.
An even more insidious source of potential contamination can occur in controlled environments, e.g., hospital and clinics, maintained to minimize the presence of pathogens in bacterial and/or viral form. As is commonly known, medications in fluid form including vaccines, often are stored in airtight containers or vials having caps with rubber membranes secured thereto. To obtain a dose of the enclosed medication, a syringe/needle assembly is used to extract the medication. The tip of the needle is pressed against the membrane to pierce it so as to allow entry of the needle. As the needle is advanced, the resilient membrane seals around the needle to prevent air infiltration in one direction and fluid escape in the other.
Although the interior of the container and the medication itself may be sterile, the outside of the container may have surface contamination. For example, the container top may be contaminated by contact transmission of pathogens or via aerial assault, e.g., a health care professional sneezing in close proximity to the container. Microscopic pathogens may be deposited onto the container including the membrane without any visible sign of the contamination. Once the syringe needle is pressed against the membrane for insertion, any contamination on the membrane can be transferred to the outside of the needle and spread along the needle as the needle is advanced through, and retracted from the membrane. Although the contents drawn into the needle and syringe may be sterile and contaminant fee, the outside surface of the needle may harbor contamination obtained from the fluid extraction process.
Unknown to the healthcare professional handling the syringe, use of the same needle to penetrate the skin and tissue of a patient to administer the medication results in exposure of the patient's internal tissues to the contaminant. What is needed is a means to ensure solutions aspired into syringes for subsequent administration are effectively free of environmental and solution-borne contaminants. What is also needed is a means to ensure a needle used for insertion into human tissue to administer medications is free of pathogenic contamination both inside and outside the needle.
Many devices and methods have been developed to address these problems, however, the shortcomings and inefficiencies of these prior attempts are considerable. For example, U.S. Pat. No. 5,125,415 discloses a syringe tip cap. The cap includes an enclosed filter for filtering air from a loaded syringe prior to administration. To use the syringe cap, a desired solution or fluid is drawn into the syringe via an attached hypodermic needle or the like. As is often the case, whatever is drawn into the syringe will include any contaminants in the solution including the aspiration of unwanted air, which, in and of itself, can be considered a contaminant, particularly if the drawn fluid is destined for later intravenous administration, or for lab testing when, for example, blood gas levels are measured if the fluid is drawn blood.
Once the syringe is loaded, the needle is removed and the cap is secured to the syringe. The plunger is then advanced down the syringe barrel while the syringe is held in a substantially vertical orientation with the connection end at the top. This allows lower density gases to migrate to the now top of the syringe where it enters the cap and passes through the enclosed filter. Once the air has been purged, the fluid contacts the filter and causes it to swell so as to seal the cap. This ensures the fluid is maintained in the syringe. The cap is then removed and the fluid is ready for expulsion from the syringe.
The drawbacks of this approach are significant and considerable. First, the cap, by design, does not allow for the flow of fluid through the filter. This prevents the filter from being used to filter any non-gaseous contaminants out of the contained fluid. Second, the cap requires the needle to be removed to perform the filtration step and later re-attached, or replaced with a new needle for further use. This adds considerably to the possibility of a needle stick event due to the need to handle the needle portion multiple times for one use.
Another approach taken is disclosed in U.S. Pat. No. 3,859,999. In the '999 patent, a single filament is rolled and intertwined into a wad. The wad is placed at the bottom of the syringe barrel or in a bore formed in a needle holder so as to place the wad between the connected fluid channels of the needle holder and the connection end of the syringe. This approach has a similar deficiency to that of the '415 patent in that the needle remains exposed throughout the series of steps taken to load the filter and operate the syringe. The chances for a possible needle stick event are numerous.
U.S. Pat. Appl. Publ. No. US 2008/0097353 discloses a filter secured in a distal end of a syringe needle having frangible sections. Fluid is drawn into the needle and attached syringe through the needle tip. The filter disposed behind the needle tip filters the incoming fluid. Once the fluid has been aspirated to the desired amount, the needle tip including the filter is detached by snapping the needle at the frangible section located behind the filter. The needle tip and filter are thereafter discarded. The section of the needle remaining after the separation has a properly shaped new tip for tissue penetration. Although this approach solves the problem of filtering fluids before entry into the syringe, the constantly exposed needle combined with the manual method used to remove the needle tip presents a constant danger of a needle stick event.
A yet further approach to solve contamination problems with aspirated fluids is shown in U.S. Pat. No. 4,066,079. The '079 patent discloses a filter apparatus that attaches to a syringe at one end, and to needle at the opposing end. The filter apparatus defines a pair of chambers, each having a one-way check valve. One valve is dedicated to permit fluid to flow into the syringe, while the other is dedicated to allow fluid to flow out of the syringe. A filter is lodged behind the outward bound check valve to filter the contained fluid as it flows out of the syringe. Although this system requires less manipulation of the needle, it still presents the problem of an exposed needle with the possibility of a needle prick event. Moreover, part of the chamber through which the fluid is drawn into the filter apparatus contacts the fluid after filtration, but before entry into the hilt of the needle. Any contaminants deposited in the shared chamber can be reintroduced into the fluid as it exits the apparatus into the needle. This counteracts and defeats the purpose of the filter secured in the apparatus to eliminate contaminants before injection of the intended fluid.
A still further approach is disclosed in U.S. Pat. Appl. Publ. No. 2009/0264829 in which a needle sheath with a filter plug secured to a distal end is disclosed. In this apparatus, the sheath encloses the needle and allows for the aspiration of fluid through the filter and into the needle. In one embodiment, the needle tip enters the filter and receives fluid directly through the filter. The tight-fitting sheath allows for the creation of a vacuum in the sheath to promote fluid flow into the needle and syringe. Once the syringe is loaded, the sheath is removed and the syringe is ready for use. Although this approach solves the problem of an exposed needle, it requires the sheath to be fitted to the specific syringe and needle, which can differ considerably with respect to syringe barrel width as well as needle length. Moreover, the design allows for the needle to pierce the filter and has no means to prevent the extent to which the needle pierces the filter.
What is needed and what is provided herein is a universal needle filter assembly that effectively eliminates fluid contaminants from being drawn into a syringe and protects against needle stick events regardless the size and structure of the syringe and/or needle. What is further needed is a disposable needle filter assembly that includes features to completely enclose a syringe needle and a means to create a substantially airtight chamber to allow for the effective aspiration of fluid through the filter and into the syringe in an aseptic, substantially pathogen-free and contaminant-free manner. What is also needed is a needle filter assembly that incorporates a needle stop surface to prevent a syringe needle from penetrating the needle filter when engaged with the needle filter assembly. These and other objects of the disclosure will become apparent from a reading of the following summary and detailed description of the disclosure as well as a review of the appended drawings.